Manufacture of gun-tubes and like tubular bodies



R. A. HADFIELD, A. G. MAcK. JACK AND A. B. H. CLERKE.

MANUFACTURE OF GU'N TUBES AND LIKE TUBULAR BODIES APPLICATION FILED MAR.28. I918.

ISHEETSSHEET l.

1,365,987. Patented Jan. 18, 1921.

R. A. HADFIELD, A. G. MACK. JACK AND A. B. H. GLERKE.

MANUFACTURE OF GUN TUBES AND L|K-E TUBULARBODIES APPLICATION. FILED MAR.28. 1918.

T SHEETS-SHEET 2.

1,365,987. Patented Jan. 18,1921.

H. A. HADFIELD, A; G. MACK. JACK AND A. B. H. CLERKE.

MANUFACTURE OF GUN TUBES AND LIKE TUBULAR aomes APPLICATION F|LE D MAR.28, I918 Mme ' 7 Patented Jan. 18, 1921 I I APPLICATION FILED MAR. 28

if x 7/// ///Jfl7//// ww mm m W. m HwW n //A/ v R. A. HADFIELD, A. G.MAcK. JACK AND A. B. H. CLERKE.

MANUFACTURE OF GUN TUBES AND LIKE TUBULAR BODIES APPLICATION FILED MAR.28, I918.

1,365,987. U Patented Jan. 18,1921.

7 $HEETS-SHEET 5.

R. A. HADFIELD, A. G. MACK. JACK AND A. B. H. CLERKE.

MANUFACTURE OF GUN TUBES AND LIKE TUBULAR BODIES APPLICATION FILED MAR.28. 1918.

1,365,987. Patented Jan. 18,1921.

ISHEETS-SHEET 6.

R. A. HADFIELD, A. G. MACK- JACK AND A. B. H. CLERKE. MANUFACTURE omumTUBES -AND LIKE TUBULAR BODIES APPLICATION FILED MA R. 28, 1918-1,365,987.

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st: Inventor:

- fibtr?fl.h'al feld 41: 106. Jam? by flgiwamawmv Atty Patented Jan. 18,1921.

UNITED. STA ES PA NT OFFICE.-

nonnnm ABBOTT nnnrmnn, or w'nsrmns'rmi, AND ALEXANDER exciton nxcxmrzmmax AND nu'eus'rus BASIL 1mm cLmE, or, SHEFFIELD, ENGLAND.

manumc'runn or eon-Tunas AND uxn ruminant ooms;

, Specification of Letters Patent Patented Jan, 18, 1921,

Application filed March as, 1918. Serial No. aaarza To all whom it mayconcern:

Be it'known that we, RGBERT ABB TT HAD- FI LD and ALEXANDER GEORGEMACKENZIE Jncn and AUGUSTUS BASIL Hon'r CLERKE, subjects of theKing ofGreat Britain and Ireland, residing, respectively, at the city ofWestminster, England, Sheffield, in the county of York, England, andSheffield, in the county-of York, England, have invented improvements inthe lldanufacture of Gun. Tubes and like Tubular Bodies, of which thefollowing is a specification.

This invention has reference to the manufacture of gun tubes, suitablefor use in the construction of howitzers and like guns and also for useas linings for heavier and longer. guns, such for example as wire woundor built up guns, in such a manner that they can be easily and quicklymade without the use of a steam hammer, hydraulic hammer, rolling millor forge, so as thereby to eflect not only a great reduction in the costof production of such gun tubes but also considerable saving in time ofproduction, and enabling engineering Works unprovided with plant of thekind referred to, to be quickly adapted for the manufacture of such guntubes, features of great practical and national importance under thepresent war conditions.

According to the invention, a gun tube is produced by casting a steelingot of suitable diameter and length to provide sufficient metal forthe required finished gun tube then, after allowing it to cool andremoving the head or discard therefrom, subjecting the resulting blankor billet while at a suitable temperature to a hollow extrusion processconsisting in piercing a central hole in it by means of a punch while itis supported externally and at one end within a matrix or container(hereinafter "called the matrix) having a cylindrical interior ofthe'same diameter as the external diameter of the blank or billet sothat the blank or billet being unable to expand radially to a greaterdiameter than that of the interior of the matrix, when subjected to thepiercing action of the punch, is constrained to flowlengthwise betweenthe punch and the. -matrix,- the-diameter of the punch,;the internaldiameter ofthe matrix and the travel of the punch being such as toproduce a hol-- low extruded blank or billet (hereinafter called fordistinction the extruded blank) closed at one end and of materiallygreater 7 length than the original blank or billet from which it wasmade. The extruded blank thus made from the cast ingot' is thensubjected to successive drawing operations by forcing it through drawdies or sets of draw dies 0 successively decreasing diameter bysuccessive mandrels each of materially smaller diameter than theinternal diameter of the extruded blank and of the partly formeddrawn'gun tube made therefrom, ex-

' cept, it may be, the mandrel used for eifecting the final drawing,so'that the extruded blank and also the partly formed. gun tube is,while it is being passed through the dies, except, it may be in making aspecial form as hereinafter described, the finishing die or r set ofdies, and is'exposed to the constricting action of such dies, free tocontract in diameter internally, with the result that the external andinternal diameters of the extruded blank and of the partly drawn guntube, are both reduced simultaneously with elongation of the tube as awhole. In this way the maximum amount of useful work can be done on themetal of the extruded blank and drawn gun tube and this work will beevenly distributed all around the metal under treatment. y

In order to prevent each drawing vmandrel pushing its way through theclosed end or base of the heated extruded blank and gun tube duringdrawing, the closed base end of the blank and of the gun tube is cooledby a suitable cooling medium preparatory to commencing each drawingoperation. For this purpose'the base maybe cooled by directing a jet ofwater upon it for a suitable time, depending upon the mass of metal insuch end.

It is important that the form of the inner end of the bore or hole inthe forging, forming the seat for the drawing mandrel, should be moresteeply arched than the head or forthe head of each being of a moreflattened form than the seat into which it takes. If the bore and seatof the extruded blank firstproduced should be found to be eccentric tothe exterior of the blank, the said blank should, after cooling, bemachined, as in'a lathe to make the several parts mentioned concentricto one another before subjecting it to the drawing operations. Theextruded blank is then reheated to a suitable drawing temperature anddrawn through dies to form it into agun tube of the required length andexternal diameter, the tube being reheated prior to the successivepasses through the dies as is usual in tube drawing processes.

.The finally drawn gun tube is then cut to length, rough turned andbored to a pproximatel the required finished dimensions to form ahowitzer or likegun, or, if it is to be used as a. lining for a gun, itsclosed end is .cut'ofi'. The gun or gun tube is afterward subjected to asuitable heat treatment such as hereinafter described, to impart to theIllGtfll of which it is composed the desired mechanical properties toadapt it for practical use. The gun tubei is finally machined to therequired fin shed dimensions.

In carrying out the invention the caststecl' ingot from which the guhtube is produced may advantageously be made with a longitudinallygrooved exterior surface, the grooves being of concave shape and ofgradually increasing radial depth as they proceed from the upper totheilower portion of the, ingot,

with the outer edges or surfaces of the ridges between the groovesparallel, or nearly so, to the axis of the ingot and of rounded orconvex shape.

Such a grooved formation of the exterior of the ingot results in theproduction, in effect, of a taper ingot having a cooling surface that isvery large in area at the lower to cooling and other portion ofthe ingotand gradually decreases in area in the upward direction. By this means,after casting such an ingot, the molten metal will solidify quickly atthe bottom and more slowly in an upward direction, so

that molten metal at the top can descend.

andcompensate for shrinkage of metal due causes and prevent theformation of blow holes, pipes and the like, with the result that aningot of sound homogeneous steel,-which is very essential in theproduction of reliable gun tubes, is obtained. Owing to the outer edgesor surfaces of the ridges being parallel or nearly parallel to the axisof the ingot, the blank or billet obtained by removal of the head anddiscard of the ingot, can be readily centered in a true manner in theextrusion matrix in which it is placed preparatory to beingsimultaneously pierced and extruded, so that the hole formed in theresulting extruded blank shall be concentric with the exterior of theblank. The longitudinal grooves in the blank or billet are-graduallyeliminated ,to a greater or less extent by radial flow .of the metal,during the punching andextrusion of the blank or billet or during thisprocess and the subsequent drawing of the resulting extruded blank intoa gun tube. a

ess.

The dies used for drawing the extruded be made of cast iron with theinternal face chilled, and be of the usual flared shape. l Vith thisform of die the extruded billet and partly formed gun tube can bereduced in diameter to the extent at least of about .625 inch at eachpass.

Gun tubes produced as described can be made from steel of various kinds,as for instance, carbon steel, nickel steel or nickel chromium steel andbe heat treated in various ways to specially adapt them for use.

In order that the invention may be more readily understood it will'nowbe further described with the aid of the accompanying drawings withreference to the manufacture of a trench howitzer or like gun and to themanufacture of a gun tube suitable for use as a lining for an ordinarywire-wound gun of greater strength and length than a howitzeror likegun.

In these drawings, Figure lshows, by way of example, a longitudinallygrooved cast steel ingot of the kind herein referred to. Fig. 2 showsthe ingot after the removal of its head or discard portion, shown in dotand dash lines, to form a solid blank or billet. Fig. 3 shows the hollowextruded blank produced by extrusion of the solid blank or billet andFig. 4; shows the gun tube obtained by drawing the extruded blank. Fig.5 shows a finished muz zle loading trench howitzer, say a6 inchhowitzer, after the drawn gun tube, shown in Fig. 4, has been roughlymachined to shape, heat treated and finally machined to the requiredfinished dimension and provided with external appliances to adapt it foruse.

Figs. 6, ,7, 8, 9 and 10 are similar views to Figs. 1, 2, 3, '4.- and 5respectively, showing, by way of example, a cast steel ingot and thesuccessive stages in its conversion into a. gun tube suitable for use asa lining for say a 9.2 inch breech loading howitzer gun.

Fig. 11 shows partly in plan and partly in longitudinal section on theline A A of Figs. 12 and 13, a longitudinally grooved blank or billetready for extrusion. Figs. 12 and 13 are respectively left and righthand end views of the blank or bi]- let showrt in Fig. 11. Fig. 14 showsin longitudinal vertical section the extruded blank produced bysubjecting the blank or billet shown in Figs. 11, 12 and 13 to thesimultaneous piercing and extrusion proc- Figs. 15, 16 and 17 show thesuccessive results of subjecting -the extruded blank to three successivedrawing operations. Fig. 18 shows in longitudinal section, a gun tubeproduced by cutting the drawn gun tube shown in Fig. 17 to length andboring and turning it to approximately the desired finished dimensions.

i Fig. 19 shows partly in side elevation and partly in section, and moreor less diagrammatically, and to asmaller scale than the precedingfigures, plant 7 for simultaneously piercing and extruding a cast steelblank or billet, the resulting extruded blank being shown inlongitudinal section. Fig. 20 is a cross section on the line A A of Fig.19. Figs. 21, 22 and 23 are similar views to Fig. 19 showing thedrawing'plantand three stages in the conversion of the extruded blankinto a gun tube. Fig. 24 shows the drawing plant in side elevation andhow the mandrel used therein can be tilted upward to allow of the partlydrawlt'gun tube being slippedon such mandrel before forcing it through asucceeding set 'ofdraw dies to complete its conversion into a gun tube,

the mandrel in this figure being shown. smaller than the internaldiameter of the hollow blank. Figs.'25 to 32 are detailed viewsillustrating successive stages of the drawing operation more clearly to.illustrate the provision of clearance between the dies and mandrels topermit of unobstruct-' ed inward working-of the metal of the tube as itis reduced. Fig. 25 is a partial, longitudinal, sectional viewillustrating'an intermediate stageof the drawing operation showing thetube entering a die of one, of

the passes, and Fig. 26 is a vertical cross [I section through the dieand mandrel of F 25-. Figs. 27 and 28 are similar views illustrating thetube or tube blank as fully reduced by said pass, and emerging from thefinal die thereof. Figs; 29 and 30 are longitudinal and sectional viewscorresponding to Figs. 25 and 26, illustrating the entry of the-reducedblank, as it comes from the die of Fig. 27, into the foremost die of thefinishing pass as illustrated in Fig. Figs. 31 and 32 are viewscorresponding to.

Figs. 27 and 28 illustrating the complete tube as it emerges from lshefinal reducing The following is a typical example of the.

manner and means adopted for producing a 5111 tube according to theinvention.

solid steel ingot a (Fig.1 or Fig- 6) is cast with a considerablenumber, say. twelve, of longitudinal grooves b of gradually increasingradial depth from the upper to the lower portion of thevingot and ofconcave shape in cross section, the intervening ribs 0 having theirouter surfaces of rounded shape and substantially but not quite parallelto the axis of-the ingot as :and for the purposes hereinbeforedescribed, the

overall'shape of the ingot in end view being of a cylindrical character.The outer surfaces of the ribs, as cast, are not quite parallel to theaxis of the ingot in order to provide sufficienttaper to'enable theingot to be readily removed from its mold aft'er casting. The grooves 11may extend part of the length of the ingot, theremaining portion'of theingot being our lindrical shape, as in Fig. 1, or they may extendpractically throughout the length of .the ingot as in Fig. 6.- The heador discard portion '03 of the ingot is cut oil" and the remainingportion of the ingot roughly turned to the same diameter throughout toform a blank or billet (see Figs. 2 and 7) that will accurately fit thematrix of the extruding plant. This plant comprises a powerful hydraulicpress c, a heavy stationary casting 7' provided with a number ofvertical grooves 9 arranged parallel to one another, a cylindricalmatrix it having about 1200 (3., if it is made of carbon steel,

or say to about 1130 C. if made of nickel steel or nickel chromiumsteel. It is then placed in the matrix h and aga nst- -the.plug 70supported by the abutment m,

the internal diameter of the matrix being equal to that of the blank a.The punch a, which is of a diameter considerably greater than theinternal diameter of the. finished gun tube required, is then forcedendwise into" the blank or billet a andthe displaced metal caused toflow outward be tween thepunch and'the matrix, the inner end of theblank or billet being forced into the concave recess in the adjacent endof the plug is and the travel of the punch being limited to form aclosed end a of any desired thickness to the hollow extruded blank athus formed by the combined piercing and extrusion process. The punch ais then drawn back, the block or abutment m and plug is removed and theextruded blank a pushed out of'the matrix h by the pusher 19. Fig. 14shows to a larger scale, an extruded blank thus produced. v

The extruded blank thus obtained is then subjected to the drawingprocess to convert it into a gun tube.' The plant used for this purposecomprises as shown in Figs. 21, 22 and 23, a hydraulic press 6 astationary casting f formed with vertical grooves 9 aset of draw dies 1"adapted to fit the grooves 9 in the casting f and a .mandrel 91connected to the ram 0? of the hydraulic press c. The hydraulic press. cand casting f with grooves (Figs. 19 and 20) used for the piercing andextruslon process, may also be afterward used for the drawing process,the matrix It with plug 72 and abutment block mused for the formerfprocess, being replaced by the draw dies 1* or the latter process.

- For drawing the extruded blank a into a gun tube, it is heated to asuitably high temperature, say for example, to about 1050 to 1200 (1,then slipped over the drawing mandrel n which is made of materially lessdiameter than the internal diameter of the extruded blank 00 and then,aftep first cooling the closed end a of the blank by a jet of water forthe purpose hereinbefore mentioned, it is forced by the mandrel throughthe first set of draw dies 1' (see Fig. 21). The partly formed gun tubea (see Fig. 15) thus obtained is then reheated,its closed end cooled asbefore and then forced by another and smaller mandrel n through a secondset of dies 1' (see Fig. 22). The partly formed gun tube a thus obtained(see Fig. 16) is then reheated, its cldsed end-cooled as before, andthen forced by another and smaller mandrel 02, through a third set ofdraw dies 1' (see Fig. 23). Fig. 17 shows the resulting drawn gun tubea.

The man-drels n if, a used for the successive drawing operations areeach materially smaller in diameter than the internal diameter of theextruded blank a and partly drawn guntube a (L as and for the purposehereinbefore explained. The forward end of each mandrel n n", n is madeof. a more flattened form than the.

seat 8 in the extended blank a (Fig. 14) and partly drawn gun tube,Figs. 15, 16

and 17,.into which it takes, .also as and for the purpose hereinbeforementioned.

The number of reheating and passes of the partly drawn gun tube throughsets of dies will vary according to requirement. Fora trench"'howitzersuch as' shown in Fig. 5, two passes may suflice. 'F or a longer guntube, such'as shown in Figs. 10 and 18, three passes may suffice.

In carrying. out the drawing operation, a drawing mandrel may be usedwhich, instead of being rigidly fixed to the movable ram head 0 of thedrawing press, may, as shown in Fig. 24, be jointed to such head, as bya ball and'socket joint at, so as to allow the extruded blank (1, orpartly drawn gun tube, when slipped over it, to

, center itself in the dies during the drawing operation. At the sametime, this arrangement allows, with drawing apparatus of given length, amuch longer extruded blank and gun tube to be dealt with than when themandrel is rigidlly fixed to the ram head as usual. Such mandrel can, as

shown in Fig. 24, be tilted upward by the ram "u ofa small hydrauliccylinder v mounted on a carriage w arranged to run along the bed as ofthe drawing apparatus, or by equivalent lifting means, into aposition,'indicated in dotted lines, to allow of the extruded blank, orpartly formed gun tube a, being slipped endwise on to the mandrel clearof the dies 1' and then lowered into position to allow of the extrudedblank or partly drawn gun tube being pushed through the dies to effectthe drawing operation. The head y of the lifting ram 14 or equivalentlifting means, may be adapted, as by forming it of a suliicient widecrutch shape, to allow of the mandrel being swung to one or other sideof the center line of the press and dies when this may be desire In somecases the external diameter of one end of a gun tube may require to belarger than the remainder of the tube, or a tube with steps in itsdiameter may be required. In such cases the gun tube may not be allowedto pass entirely through the (lies during some of the final draws butonly to a sufficient extent as is necessary to produce the requiredresult, the draw being stopped at the required point, the mandrelwithdrawn and the gun tube pushed back through the dies, as by means ofa hydraulic extractor ram, such as p in Fig. 23, with the aid ofsuitable extension pieces. Or the required enlargement or steps may beleft on the gun tube by suitably turning the drawn gun tube in a lathe.

For a trench howitzer, the drawn gun tube retains its closed breech endand is rough bored and turned approximately to the required finisheddimensions (see Fig. 5). For a lining for a gun, the closed end of thegun tube is cut off and the tube rough bored and turned approximately tothe required finished dimensions (see Figs. 10 and 18). The forwardportion (1 (Figs; 1 and 9) of the drawn gun tube which is cut off, canbeused for testing purposes.

The gun tube thus produced and machined approximately to shape, is thensubjected to heat treatment to impart the desired physical properties toit to adapt it for use. For this purpose the gun tube is heated to ahigh temperature and cooled by quenching it in a suitable coolingliquid, as for example oil or water. It is then reheated to a lowertemperature than that of the first reheating and then cooled in water orin air or in the heating furnace. For example, if the gun tube is madeof carbon steel containing say about 38% 'carbon, about .89% manganeseand low in silicon, sulfur and phosphorus, it ma advantageously beheated to about 900 and dipped vertically breech end first into oil,then reheated to about 640 to 660 C. and quenched in a similar manner inwater, then reheated to about 670 to 680 C. and

allowed to cool in air. In the case of a gun tending through the blankand acting at the chromium, it may be heated to about 850C.

then uenched in oil, then reheatedto about 650 and quenched in water orit may be heated to about 640 to 650 C. and allowed to cool in the air,or it may be reheated toabout 650 C. to 670 C. and allowed to cool intheair.

The heat treated gun tube is then ma-- chined to the desired ,finaldimensions for use.

What we claim is:

1. The method of. producing gun tubes and like tubular bodies whichconsists in forcing a hollow blank having a closed end through dies bysuccesm've mandrels which act against the closed end only of the blankand "are of substantially smaller diameter than the interior of theblank at the part thereof being acted upon by the dies at their smallestinternal diameters so that the metal of the blank at these parts isunsupported internally and free to be moved radially inwardsimultaneously with elongation of the blank as a whole.

2. The method of producing gun tubes and like tubular bodies whichconsists in forming a hollow cylindrical blank closed at one end andhaving a substantially cylindrical bore of larger diameter than that ofthe required finished tubular body, heating the said blank, cooling itsclosed end, and forcing the blank through a die by amandrel exclosed endonly-thereof and of a. dlameter such that the metal of the blank, whileit-is being forced through the smallest part of the die and is exposedtothe constricting action thereof, is free to move radially inward so thatthe external and internal diameters of the blank are both reducedsimultaneously with elongation of the said blank as a whole.

3. Themethod of producing gun vtubes and like tubular bodies whichconsists in forming a hollow cylindrical blank closed at one end andhaving a substantially cylin drical bore of larger diameter than thatofthe requiredfinished tubular body, by piercing a solid metal blanksupported externally and at one end so that thewall of the hollowblankis produced by extrusion of metal,

heating the saidblank, cooling its closed end and forcing the hollowblank through dies by mandrels of substantiallysmaller diameter thanthat of the "interior of the hollow blank and acting against the closedend only of the/blank, so that the metal of the blank while it is beingforced through the smallest ally inward simultaneously with elongation Iof the blank as a whole.

4. The method of producing a gun tube, liner, howitzer or the likeproducing a cast metal blank of substantially. the same overall diameterthroughout its length, placing the blank in a die of substantially thesame diameter internally, piercing the ingot centrally and subjectingthe hollow extruded blank thus formed and while in a heated condition tothe action of dles through which it is forced by mandrels ofsubstantially smaller diameters than the internal diameter of the blank,so that the metal of the blank is caused to move simultaneously inradiall inward and longitudinal directions whi e passing through thesmallest part of the dies."

5. The method of producing a gun tube,

which consists in y liner, howitzer or the like, which consists inforward, and subjecting the extruded hol- I low blank thus formed andwhile in a heated condition to the action of mandrels and dies in suchmanner that the metal is unsupported internally in the plane'of greatestconstriction by the dies so that it is free to be displaced radially inan inward direction to reduce theinternal and external diame' ters ofthe tube simultaneously with elongation of the tubeas a whole.

6. The method of producing gun. tubes, liners, howitzers, etc., vwhichconsists of forming an ingot with longitudinal tapering grooves butwhose diameter is substantiallythe same throughout its length, plac ingthe ingot in a matrix of substantially the same diameter, piercing theingot mm 3 trally, and subjecting the blank thus formed to the action ofmandrels' and dies so that the metal is radially displaced to elongate.the tube and reduce its internal and external,

diameters.

' '7. The method of manufacturing a gun tube or the like which, consistsin placing a solid cast steel blank" in a heated condi-' tion within adie closed at one end,,piercing the blank centrally and thereby causingthe. a

metal of the blank to flow longitudinally.

between the die and punch to form. a hollow extruded blank of materiallygreater lengththan the said solid blank and closed at one end andforcing the said extruded. blank while in a heated condition-throughsucces-.

sive dies by mandrels of materially less diameter than the internaldiameter of the blank and acting against the closed inner end only ofthe blank so that the metal is free to flow radially inward during .suchoperation while the blank is being elongated as a whole. 7

8. The method of manufacturing a gun tube or the like direct from asolid cast steel blank of substantially the same overall diameterthrolighout its length by placing the blank in a die of substantiallythe same diameter, piercing the blank centrally, while heated, to form ahollow extruded blank closed at one end and of materially greater lengththan the solid blank and forcin the extruded blank, while heated,through succentrally while in a heated condition and thereby causing themetal thereof to flow radially outward and longitudinally for,- wardbetween the die and punch to form a hollow extruded cylindrical blank ofmateriallygreater length than the said solid blank and closed at oneend, reheating the said blank, cooling its closed end and forcing itthrough dies by successive mandrels applied to the closed inner end onlyof the blank and of substantially smaller diameter than the interior ofthe blank and thereby causing inward radial displacement of metalsimultaneously with the constriction of the external diameter andelongation of piercin the blank to form the desired gun tubes.

10. The, method of manufacturing a gun tube or the like, which consistsin forming a solid cast steel blank .with longitudinal grooves in itsperiphery ofconcave form in cross section and with the edges of theridges between the grooves of rounded shape and substantially parallelto the axis of the ingot, placing the said blank while at a forg ingtemperature, within a die of the same diameter and closed at one end,centrally the said blank to form a hollow cylindrical extruded blankclosed at one end and of materially greater length than the 1 solidblank operated upon and forcing said extruded blank-while in a heatedcondition 'with its closed end in a cooled condition through successivedies by mandrels acting against the closed inner end only of the blankand of materially smaller diameter than the internal diameter of theblank for the purpose set forth.

11. The method of manufacturin a un tube or the like, which consists inormlng a solid cast steel blank of substantially the same overalldiameter throughout its length,

placing the said blank at a forging temperature centrally within a dieclosed at one end, piercing the blank centrally in a longitudinaldirection to produce a hollow extruded blank closed at one end and ofmaterially greater length than the blank or billet operated upon, and ofcylindrical shape both externally and internally, forcing the extrudedblank while heated and with its closed end in a cooled condition, throuh successive dies to form a un tube of the desired length by mandrels 0%materially smaller diameter than the internal diameter of the blank andacting a ainst the closed cooled end only of the blank, for the purposeherein set forth and subjecting the resulting gun tube to heat treatmentto remove strains set up therein by the foregoing mechanical treatmentand to impart desired physical characteristics to the said tube. a

12. The method of manufacturing a gun tube or the like, which consistsin forming a solid cast steel blank with longitudinal grooves in itsperiphery of gradually increasing radial depth toward oneend and ofconcave shape in cross section with the edges of the ribs between the'grooves of rounded shape and substantiall parallel to the axis of theingot, placing the said blank in a heated condition within a die of thesame diameter as the blank and closed at one end, piercing the blankcentrally to produce a hollow extruded blank of c lindrical shape bothexternally and interna ly and closed at one end and of materiallygreater length than the blank operated upon, forcing the extruded blankwhile heated and with its closed end in a cooled condition, throu hsuccessive dies to form a gun tube of the esired length by mandrels ofmaterially smaller diameter than the internal diameter of the blankbeing operated upon and acting against the closed cooled end only of theblankfor the purpose herein set forth, and afterward subjecting theresulting gun tube to heat treatment consisting in heating it to a hightemperature, then quenching it in a cooling liquid then reheating it toa lower temperature than that to which it was first heated beforeuenching and cooling it. 1 13. The m'et 0d of manufacturing a gun tubeor the like from a nickel chromium steel blank according to-claim 11,wherein the heat treatment of the resulting gun tube consists in heatingthe said tube to a temperature of from about 850 C. to 900 C, dipping ittube consists in base end downward ;into,oil,'to quench it, reheating itto a tein perature of from about 640? C. to 680 C. and cooling it. Y

14. The methodof manufacturing a gun tube or the like from a nickelchromium (steel blank according to claim 11, wherein the heat'treatment' of the resulting gun ,heating the said tube to about 850-0., dipping it base end downward," into oil; to quench it, reheating itto about 650 C. and quenching it, base end downward in ,Water. I

15. The method of producing gun tubes and like tubular bodies whichconsists in forcing a hollow blank having a closed end through dies bysuccessive mandrels which act against the closed end only of the blankand -are of substantially smaller diameter than the interior of the.blank at the partthereofbeing acted upon by the dies at their smallestinternal diameter so that the metal of the blank at these parts isunsupportedinternally and free to bemoved radially inward simultaneouslywith elongation, the bore of the-blank at its inner end beingv formedwith a curve of larger radius than the head or forward end of themandrel whereby the latter will center itself with relation to" theblank, substantially as described. l

16. The methodof producing gun tubes and liketubular bodies whichconsist in' forming a hollow, c lindrical blank closed at one end andhaving "a substantially cylindrical bore of larger diameter than that ofthe required finished body, heating the said blank, cooling its closedend, and forcing the blank, through a die by a mandrel.

extending through the blank and acting at the closed end only thereofand Mia 'diameter, such that themetal of the blank, while it is beingforced through'the smallest part of the die and is exposed to theconstricting actionthereof, is free to move radially inward so that theexternal and internal diameters of the blank are both reducedsimultaneously with elongation of the said blank as a whole said blankhaving its bore at its inner end formed tapering with ,relationito heador forward end of the mandrel wherebv the latter will center itself withrelation 7 to theblank, substantially as described.-

17. The method of producing gun tubes and like tubular bodies whichconsists in HADFIELD, on the ALE NDER forming a hollow cylindrical blankclosed at one end and having a bore oflarger'diameter than that of therequired finished tubular body and subsequently developing the blank tosubstantially finished form wholly by successive drawing operationsunder the action of externally acting dies only where ,by the blank willbe reduced to approximately finished form by constriction with themaximum degree of compressing working of the metal inwardly free ofcontact internally with a cooling surface substan tially as described.

18. The method of producing gun tubes and like tubular vbodies whichconsists in initially forming a hollow cylindrical blank closed at oneend and having a substantially cylindrical bore ofi larger diam- .eterthan that of the required finished tubular body and developing the saidblank to a substantially finished formwholly by successive' drawingoperations under the'action of externally acting dies by forcing theblank though the dies by a mandrel extending through the blank andengaging at the closedend only thereof and said mandrel being of suchdiameter that the -metal of the tubular wall of the blank as it isreduced in'diameter'is free tomove radially inward to the maximum degreefree of cooling contaot'with the mandrel and free of compression betweenthe mandrel and, die substan- February, 1918. I

s Au'cus'rus BASIL 1101.1 CLERKE. A

Witnesses as to the signatures of Robert Abbott Hadfield and AugustusBasil vHolt APF'. BARTLETT, H. PETER VEN-N. I Witness as to thesignature of Alexander BURDiiKIN.

-George M cKenz ie Jack:

a B. i

BASIL Hour CLERKE, on the 20th day of

